Carbon nanotubes have optimal properties, such as high conductivity, high aspect ratio and high mechanical strength, for numerous applications. In the production of electrodes for the development of, for example, novel touch screens, photovoltaic panels and light-emitting diodes, the production of transparent, conductive and flexible electrodes is a major challenge because current technologies use costly and brittle inorganic oxides. For example, films formed from compositions containing inorganic oxides (such as indium tin oxide films) have good conductivity but are brittle and expensive to produce. Carbon nanotubes are viewed as potential alternatives to inorganic oxides in numerous applications, such as in the development of a coating composition for coating a substrate. Since carbon nanotubes have a high aspect ratio and excellent mechanical and electrical properties, they can form conductive networks at low density on flexible surfaces and thus form a film that has an optimal balance of conductivity and optical transparency properties.
However, in the case of, for example, a coating composition containing carbon nanotubes for coating a substrate, existing compositions containing carbon nanotubes can be difficult to apply on substrates in the manufacturing process and may not be suitable for forming a homogenous film having a combination of desired properties. For example, when manufacturing a film using a carbon nanotube composition and sulfonic acid in a filtration process without the use of a surfactant, manufacturing equipment and materials may be damaged and a filtration process is difficult to apply in mass production. Further, due to the hydrophobic surface of carbon nanotubes, a surfactant is needed in order to disperse the carbon nanotubes. However, as another example, when manufacturing a film using a carbon nanotube composition and a surfactant, a homogenous film having good flexibility and conductivity can be formed but it may be difficult to remove the surfactant from the carbon nanotubes at the end of the manufacturing process. In addition, it is difficult to use a carbon nanotube composition to form a homogenous film having good wettability characteristics on a substrate, such as a plastic substrate. For example, when a carbon nanotube composition and a surfactant such as Triton™ X, sodium dodecylbenzene sulfonate (SDBS) or sodium deoxycholate (DOC) are used to form a film on a plastic substrate, these surfactants are unable to effectively lower the surface tension and thus fail to avoid dewetting effects. Accordingly, it is desired to obtain a carbon nanotube film that can be homogenously applied on a substrate, such as a plastic substrate, where the carbon nanotube film has excellent flexibility and conductivity properties, good optical transparency and improved wettability characteristics.